I too have been guilty of carrying the .22/.25 caliber “mouse guns” and agree that in some cases they might be effective for self defense. Either will kill someone, it may be the death occurs three weeks later as a result of infection, they wounded the perp, but did they really defuse the situation?
Keep in mind, if you need the weapon you are carrying, then generally your life is on the line, you want to stop the threat immediately! A larger caliber with higher capacity will serve to defuse a threat much better than a .22 derringer. There are a lot of things that influence the selection of a personal defense weapon, first and foremost should be how effective is the gun if I need it to defend myself or my family.
Bottom line…………using a “mouse gun” for personal defense is kind of like taking a knife to a gun fight. While I agree they make excellent back-up guns, they should never be used as a first line of defense.